Jesper Dangaard Brouer <brouer@xxxxxxxxxx> wrote:
> Netfilter expectations are protected with the same lock as conntrack
> entries (nf_conntrack_lock). This patch split out expectations locking
> to use it's own lock (nf_conntrack_expect_lock).
> --- a/net/netfilter/nf_conntrack_helper.c
> +++ b/net/netfilter/nf_conntrack_helper.c
> @@ -258,7 +258,7 @@ static inline int unhelp(struct nf_conntrack_tuple_hash *i,
>
> if (help && rcu_dereference_protected(
> help->helper,
> - lockdep_is_held(&nf_conntrack_lock)
> + lockdep_is_held(&nf_conntrack_expect_lock)
> ) == me) {
> nf_conntrack_event(IPCT_HELPER, ct);
> RCU_INIT_POINTER(help->helper, NULL);
Not sure if the lockdep_is_held is correct.
> @@ -399,13 +399,14 @@ static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
> int cpu;
>
> /* Get rid of expectations */
> + spin_lock_bh(&nf_conntrack_expect_lock);
> for (i = 0; i < nf_ct_expect_hsize; i++) {
> hlist_for_each_entry_safe(exp, next,
> &net->ct.expect_hash[i], hnode) {
> struct nf_conn_help *help = nfct_help(exp->master);
> if ((rcu_dereference_protected(
> help->helper,
> - lockdep_is_held(&nf_conntrack_lock)
> + lockdep_is_held(&nf_conntrack_expect_lock)
> ) == me || exp->helper == me) &&
> del_timer(&exp->timeout)) {
> nf_ct_unlink_expect(exp);
> @@ -413,6 +414,7 @@ static void __nf_conntrack_helper_unregister(struct nf_conntrack_helper *me,
> }
> }
> }
> + spin_unlock_bh(&nf_conntrack_expect_lock);
expect_lock is released here but
> /* Get rid of expecteds, set helpers to NULL. */
> for_each_possible_cpu(cpu) {
will invoke unhelp()
AFAIU unhelp() is safe in all cases even without
nf_conntrack_expect_lock being held:
* in first loop we hold nf_conntrack_expect_lock
* in 2nd loop we are holding the list lock, i.e.
if the ct is in the list it cannot disappear underneath
* in last loop you'll hold the hashed lock for the particular hash
list, so can't go away either.
So I think the lockdep annotation in uhelp is incorrect and not the
patch itself.
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